One of the most deadly plant toxins, abrin, is produced by rosary pea (Abrus precatorius). As little as of toxin per body weight will cause fatality in humans (a single seed). Birds appear to be unaffected by the deadly toxin.
The legend of the name forget-me-not: A medieval knight and his lady were walking beside a river. The knight held a bouquet in his hands. Because of the weight of the armor, he fell into the water. He threw the bouquet to her, saying, "forget-me-not.